1. Field of the Invention
The present invention relates to a cleaning method for a substrate processing system, a storage medium, and a substrate processing system. More particularly, the present invention relates to a method for cleaning a substrate processing system in which predetermined processing is performed in succession on substrates of a plurality of lots.
2. Description of the Related Art
A substrate processing system generally includes a chamber for housing a wafer as a substrate, generates plasma in the chamber, and performs plasma processing such as etching or CVD processing on the wafer. During the plasma processing performed in succession on wafers in the chamber, reaction products generated by the plasma processing and particles floating inside the chamber are adhered to surfaces of component parts disposed in the chamber. The substrate processing system thus regularly carries out an in-chamber cleaning treatment to clean the interior of the chamber.
In a known in-chamber cleaning treatment, a cleaning gas is introduced into the chamber, plasma is generated from the cleaning gas, and particles, etc. adhered to the interior of the chamber are etched by the plasma (see, for example, Japanese Laid-open Patent Publication No. 8-176828). During the plasma generation from the cleaning gas, a wafer remains housed in the chamber.
Usually in accordance with an operation program, a substrate processing system carries out plasma processing (hereinafter referred to as product processing) in succession on wafers in one lot, e.g., twenty-five wafers, for the fabrication of semiconductor devices or other products on the wafers. Since the substrate processing system ordinarily includes a plurality of chambers, e.g., two chambers, the product processing is carried out in each chamber on six to seven wafers per lot. Wafers in the same lot are subjected to the same product processing.
To enhance the efficiency of processing, there has been a demand that the product processing on wafers and the cleaning treatment be continuously carried out. To meet this demand, the present inventors et al. developed a first program for causing the substrate processing system to continuously carry out the product processing and the cleaning treatment for the wafers of one lot. With the first program, the cleaning treatment is performed at least once during the product processing on six to seven wafers in each chamber.
On the other hand, an amount of particles adhered to surfaces of component parts inside each chamber varies depending on contents of the product processing (type and pressure of processing gas, etc.). Therefore, the product processing on six to seven wafers assigned per lot to each chamber sometimes only results in a small amount of adherence of particles. In that case, it is unnecessary to carry out the cleaning treatment of the chamber. Nevertheless, with the first program, the cleaning treatment for the chamber is executed at least once per lot, causing a reduction in the efficiency of processing on wafers, i.e., a reduction in the efficiency of fabrication of semiconductor devices.
The present inventors et al. therefore developed a second program for performing the product processing in succession on wafers equal to or greater in number than wafers assigned per lot to each chamber, without making the cleaning treatment of the chamber. With the second program, the substrate processing system accumulatively counts, over different lots, the number of execution times of product processing in each chamber, and carries out the cleaning treatment of the chamber when the execution times of product processing exceeds a predetermined number of times. In the case of performing on wafers the product processing that only results in a small amount of adherence of particles, the cleaning treatment is carried out after successive execution of the product processing on a plurality of lots of wafers. As a result, each chamber can be cleaned in a timing in which an amount of adherence of particles reaches a given amount indicating that the cleaning treatment is to be performed.
With the second program, only one type of cleaning treatment can be set beforehand for each chamber, and the number of execution times of product processing is accumulatively counted irrespective of contents of the product processing performed on wafers of plural lots.
On the other hand, in processing wafers of a plurality of lots, the type of product processing is sometimes different between these lots. In that case, a problem is posed that the chamber cannot be satisfactorily cleaned, if the type of cleaning treatment set beforehand for the chamber is not suited to the product processing performed immediately before execution of the cleaning treatment. For example, this is the case if reaction products generated in the product processing are CF-based products, whereas the type of cleaning treatment set beforehand is suited for removal of resin deposits.
Even if the type of cleaning treatment set beforehand for each chamber is suited to the product processing performed immediately before execution of the cleaning treatment, the type of product processing performed on wafers of previous lot sometimes differs from that of product processing performed immediately before execution of cleaning treatment. In that case, until execution of the cleaning treatment, the product processing to which the type of cleaning treatment set beforehand is suited is executed a number of times less than a predetermined number of times. This poses a problem that the cleaning treatment is executed in an inappropriate condition (for example, in a state that an amount of adherence of particles is small).